This invention generally relates to golf clubs and more particularly to golf club heads having weight distributions which increase important moments of inertia of the club head while also increasing the "dynamic loft" of the club head.
Club heads employing various types of perimeter weighting have become quite common in the art, especially iron club heads or "irons" having so-called "cavity back" designs. In these club heads weight is in effect removed from the center of the club head and redistributed along the bottom of the club head, for example, or along the heel and toe portions of the club head, or around the entire periphery of the club head to produce a club head having a recess or cavity in the back. Club heads of the latter type have enjoyed considerable success since they effectively enlarge the "sweetspot" of the club head.
The "sweetspot" of the club head is generally regarded to be that area on the striking face of the club head immediately surrounding the center of gravity of the club head. By enlarging the sweetspot, perimeter weighted club heads allow golfers of all abilities to realize improved results over conventional club heads when the golfer fails to strike the golf ball in line with the center of gravity of the club head. These improved results translate into mis-hit shots that travel farther and straighter than they would if struck with a club having another conventional club head design.
Club heads are also known which include heel/toe weighting or hosel/toe weighting for reasons of improving the control of the club head during the swing and particularly at impact to produce shots which have less of a tendency to "hook" or "slice". The use of heel/toe or hosel/toe weighting on a club head increases the moment of inertia about a vertical axis through the center of gravity of the club head so that the club head is more stable when in a less than ideal orientation or position at impact. Examples of club heads employing heel/toe or hosel/toe weighting are found in U.S. Pat. Nos. 3,995,865 to Cochran et al., 4,826,172 to Antonious, and 5,078,400 to Desbiolles et al., and in UK Patent Application No. 2,170,719 to Kajita et al.
Cochran et al. disclose an iron club head having weight members embedded in the rear surface of the club head at the toe and heel portions thereof to increase the "radius of gyration" of the club head. Cochran et al. teach that the mass of the toe weight should be two to three times as great as the mass of the heel weight. Also, the weights are shown to be located on a line which angles upwardly from the center of the heel weight to the center of the toe weight and which extends through the center of mass of the club head located between the heel and toe weights.
Antonious discloses a "cavity back" iron club head having additional weight members contained in the cavity in various configurations. Some of the additional weight members, as disclosed in the embodiments of the Antonious patent, are generally located in the heel and toe portions of the club head and are said to maximize energy transfer for off-center shots and stabilize the club to provide better control with minimum loss of distance. Similar to the disclosure of Cochran et al., Antonious shows such heel and toe weights located on a line extending upwardly from the heel weight to the toe weight and passing through the "center of percussion" of the club head.
Desbiolles et al. disclose club heads having weight members placed in a lower portion of the toe and on the hosel of the club head. Alternative embodiments of the invention are disclosed with one alternative contemplating a nonuniform horizontal weight distribution having peaks in the weight distribution at the toe and, to a lesser extent, at the hosel area of the club head. In the other alternative embodiment the horizontal weight distribution is relatively uniform, however, toe and hosel weights are added to the club head to contribute to the uniform weight distribution.
UK Patent Application No. 2,170,719 to Kajita et al. shows a "wood" type club head in FIGS. 9 and 10 in which weight has been added in the hosel portion, rear portion and toe portion of the club head by "thickening" these portions of the club head. However, Kajita et al. fail to disclose the specific relationship between the centers of mass of the hosel and toe weights and the center of gravity of the club head.
Many efforts have also been made to produce a club head that aids a golfer, using a golf club with a striking face of a given loft angle, in hitting higher trajectory shots. The most common approaches have relied solely on the principle of offsetting the club head behind the shaft of the club. This can effectively produce a rearward placement of the club head's center of gravity with respect to the club's shaft and thereby cause the lowermost end of the shaft to bend more in the forward direction during the swing to increase the loft angle of the striking face of the club head at impact (that is, to increase the "dynamic loft" of the club head). One problem associated with golf clubs having offset club heads relates to the non-traditional appearance of the club head. Many golfers refuse to play with such clubs because they find the offset club head visually disruptive when addressing the ball.
Although prior golf clubs have had some success with increasing the moment of inertia about a vertical axis through the center of gravity of the club head, they have faltered in maximizing the moment of inertia about a horizontal axis through the center of gravity of the club head. These clubs have also failed to maximize both of the moments of inertia mentioned above while also effectively "backweighting" the club head, i.e., shifting weight and, likewise, the center of gravity of the club head behind the centerline of the club shaft, so as to increase the dynamic loft of the club to produce higher trajectory shots with club heads having striking faces of a given loft angle. Finally, past golf clubs have failed to significantly increase the dynamic loft of the club head while maintaining a more traditional looking club head without an extreme offset.
Accordingly, one object of the present invention has been to effect a weight distribution for a club head which significantly increases the moments of inertia about both horizontal and vertical axes through the club head center of gravity to more completely stabilize the club head at impact during mis-hit shots.
Another object of the invention has been to effectively backweight a golf club head to increase the dynamic loft of the club head at impact and produce higher trajectory shots than were heretofore possible with club heads having striking faces of a given loft angle.
Still another object of the invention has been to increase club head speed for such a backweighted club head by achieving a low aerodynamic drag through the highest portions of the club head's velocity before impact.